Desertification is the process
which turns productive into non- productive
desert as a result of poor land-management.
Desertification occurs mainly in semi-arid areas
(average annual rainfall less than 600 mm)
bordering on deserts. In the Sahel, (the
semi-arid area south of the Sahara Desert), for
example, the desert moved 100 km southwards
between 1950 and 1975.
* Overgrazing is the major cause of
desertification worldwide. Plants of semi-arid
areas are adapted to being eaten by sparsely
scattered, large, grazing mammals which move in
response to the patchy rainfall common to these
regions. Early human pastoralists living in
semi-arid areas copied this natural system. They
moved their small groups of domestic animals in
response to food and water availability. Such
regular stock movement prevented overgrazing of
the fragile plant cover.
In modern times, the use of
fences has prevented domestic and wild animals
from moving in response to food availability, and
overgrazing has often resulted. However, when
used correctly, fencing is a valuable tool of
good veld management.
The use of boreholes and
windmills also allows livestock to stay all-year
round in areas formerly grazed only during the
rains when seasonal pans held water. Where not
correctly planned and managed, provision of
drinking water has contributed to the massive
advance of deserts in recent years as animals
gather around waterholes and overgraze the area.
* Cultivation of marginal
lands, i.e lands on which there is a high risk of
crop failure and a very low economic return, for
example, some parts of South Africa where maize
* Destruction of vegetation in
arid regions, often for fuelwood.
* Poor grazing management after
accidental burning of semi-arid vegetation.
* Incorrect irrigation
practices in arid areas can cause salinization,
(the build up of salts in the soil) which can
prevent plant growth.
When the practices described
above coincide with drought, the rate of
desertification increases dramatically.
Increasing human population and
poverty contribute to desertification as poor
people may be forced to overuse their environment
in the short term, without the ability to plan
for the long term effects of their actions. Where
livestock has a social importance beyond food,
people might be reluctant to reduce their stock
WHAT ARE THE EFFECTS OF
Desertification reduces the ability of land to
support life, affecting wild species, domestic
animals, agricultural crops and people. The
reduction in plant cover that accompanies
desertification leads to accelerated soil erosion
by wind and water. South Africa losing
approximately 300-400 million tonnes of topsoil
every year. As vegetation cover and soil layer
are reduced, rain drop impact and run-off
Water is lost off the land
instead of soaking into the soil to provide
moisture for plants. Even long-lived plants that
would normally survive droughts die. A reduction
in plant cover also results in a reduction in the
quantity of humus and plant nutrients in the
soil, and plant production drops further. As
protective plant cover disappears, floods become
more frequent and more severe. Desertification is
self-reinforcing, i.e. once the process has
started, conditions are set for continual
HOW WIDESPREAD IS
About one third of the world's land surface is
arid or semi-arid. It is predicted that global
warming will increase the area of desert climates
by 17% in the next century. The area at risk to
desertification is thus large and likely to
Worldwide, desertification is
making approximately 12 million hectares useless
for cultivation every year. This is equal to 10%
of the total area of South Africa or 87% of the
area of cultivated lands in our country.
In the early 1980s it was
estimated that, worldwide, 61% of the 3257
million hectares of all productive drylands
(lands where stock are grazed and crops grown,
without irrigation) were moderately to very
severely desertified. The problem is clearly
About half of southern Africa is semi-arid and
thus at risk of desertification. The area already
transformed into desert-like conditions is not
accurately known because uncertainty surrounds
the precise definition of a desert, and what the
original state of the vegetation was in the
semi-arid areas of southern Africa.
The areas which are known to
have deteriorated this century are mainly on the
edges of the southern Kalahari. The deterioration
of the Karoo is less well established. It is
possible that desertification of the Karoo began
in the last century, when sheep were first
introduced, and before good records were
available for the area.
In recent years the
introduction of artificial water points into the
Kalahari within Botswana, together with the
widespread erection of veterinary fences, has led
to the rapid desertification of huge areas.
Similar schemes have had the same effect in the
southern Kalahari within South Africa and
HOW CAN DESERTIFICATION
To halt desertification the number of animals on
the land must be reduced, allowing plants to
regrow. Soil conditions must be made favourable
for plant growth by, for example, mulching. Mulch
(a layer of straw, leaves or sawdust covering the
soil) reduces evaporation, suppresses weed
growth, enriches soil as it rots, and prevents
runoff and hence erosion. Reseeding may be
necessary in badly degraded areas. Mulching and
reseeding are expensive practices.
However, the only realistic
large-scale approach is to prevent
desertification through good land management in
WHAT YOU CAN DO?
Desertification often occurs over many
generations, on a very large scale and so it is
difficult for individuals to take action. Some
ideas for combatting this problem include:
* Take part in the activities
of conservation groups.
* Bring overgrazing and land
mismanagement to the attention of the Directorate
of Resource Conservation (address below).
1988-89. World Resources Institute.
Basic Books, New York, 1988.
AFRICA IN CRISIS.
Lloyd Timberlake. Earthscan, London, 1991.
YOUR HEART YOUR PLANET.
H. Diamond, J. Burnham and H. Taylor. Eartheart,
Cape Town, 1991.
Agricultural Information. Department of
Agriculture, Private Bag X144, Pretoria 0001.
Tel. 012-319 7327
Director: of Resource
Conservation. Department of Agriculture,
P/Bag X120, Pretoria, 0001. Tel. 012-3197685.
The National Botanical
Institute. Private Bag X7, Claremont
7735. Tel. 021-762 1166.